One method of repairing damaged sewer pipe is to excavate the area surrounding the sewer pipe and replace the broken portion. This is a very expensive and a labor intensive solution and is also an inconvenience to residents living in the area and utilizing roadways overlying the area.
Another solution is In situ relining of sewer pipes. In situ methods typically utilize a resin coated liner which is inserted into the existing sewer pipeline and unrolled against the sewer pipe. The unrolled liner is held against the existing sewer pipe while the resin cures to form a new pipe lining within the existing pipe.
One example of such a method is shown in U.S. Pat. No. 4,366,012. In this patent, a process for installing a liner in a sewer pipe is disclosed which utilizes an elongated tube of felt coated on the exterior with urethene to form an "outer" tube. Because the felt tube is coated with this material, the two tubes act as a single integral laminated tube--with a urethane outer layer and a felt inner layer. Uncured resin is introduced into the tube and is used to impregnate the felt layer of the tube. The tube is then inverted into the end of a sewer pipe so that the impregnated felt layer is inverted to the outside and the urethane layer is located on the interior. The inversion process continues until the area of the sewer pipe needing repair has been contacted by the impregnated felt layer of the tube. When the resin cures, a pipe liner is formed by the inverted tube.
The applicant's co-pending patent application shows a method for impregnating a curable resin in a layer of resin absorbent material located within an elongated flexible bladder tube having a fill end and a vacuum end positioned down stream from the fill end. The bladder tube includes two walls forming a tube cavity therein. The layer of resin absorbent material has a down stream end positioned a predetermined distance from the vacuum end of the bladder tube, and an upstream end. An elongated gas conduit having first and second conduit ends is placed within the tube cavity with the first conduit end positioned up stream from the down stream of the resin absorbent material and with the second conduit end positioned down stream from the down stream end of the resin absorbent material.
A quantity of curable resin is then introduced into the fill end of the bladder tube, the quantity of resin being sufficient to impregnate all of the resin absorbent material within the bladder tube. A vacuum source is then connected to the bladder tube at a point spaced down stream from the down stream end of the resin absorbent material whereby the wall of the bladder tube will collapse on the layer of resin absorbent material and the gas conduit will provide a path for evaluating gas through the collapsed two walls. Gas is continuously evacuated from the bladder tube until the curable resin moves to the down stream end of the absorbent material and completely impregnates the absorbent material.
As described in detail in the co-pending '817 application, the repair sleeve is attached at its forward end to an inversion collar by means of stitches. The forward end of the inversion collar is then affixed to the forward end of the bladder tube by heat sealing, adhesive, or other suitable securement. In this way, as the bladder tube is inverted, the inversion collar will also be inverted so as to be positioned on the outside of the bladder after the inversion. Similarly, the stitches connecting the inversion collar to the repair sleeve will also cause the repair sleeve to invert, so as to be positioned on the outside of the bladder tube in contact with the portion of the pipeline to be repaired.
While the inversion collar described in the co-pending '817 application serves its purposes, it has been found that there are several drawbacks to a continuous collar connecting the bladder tube to the repair sleeve. First, the use of a continuous collar adds an additional layer of material to the bladder tube. This additional layer resists expansion when the bladder tube is pressurized to radially expand and maintain the repair sleeve in position during curing of the resin.
A second problem with the use of a continuous collar to invert the felt liner is that the collar encapsulates a portion of the liner between the collar and bladder thereby making it difficult to impregnate that portion with resin.
Obviously, the cost of material is greater with a continuous collar than with the attachment strips described herein. The strips of the present invention may be made from scrap from the manufacture of the bladder, resulting in a lower overall cost.
Another deficiency in the prior art method for inverting the repair sleeve resides in the pressures required to invert a continuous sleeve in addition to the pressure required to invert the bladder tube and repair sleeve. High pressures during the inversion process can squeeze the resin out of the repair sleeve liner, thereby decreasing the strength and durability of the repair. It is therefore desirable to decrease the amount of pressure required to complete the inversion process, as much as possible.
Another problem with prior art methods for repairing pipelines is present in pipelines of small diameter such as in laterals, wyes, and in pipelines which change diameter along their lengths. Previously, it was necessary to begin a liner at the entrance to the pipeline to be repaired, and continue the repair sleeve liner a distance to reach the repair site. If the repair site is located a great distance from the pipeline entrance, there is a great quantity of wasted material, as well as increased labor costs.